The bulbus arteriosus of the holocephalan heart

El resumen aparece en el Program & Abstracts of the 10th International Congress of Vertebrate Morphology, Barcelona 2013.Anatomical Record, Volume 296, Special Feature — 1: P-074.Previous work has shown that the outflow tract of the elasmobranch heart, namely the cardiac portion intercalated between the ventricle and the ventral aorta, does not consist of a single component, the conus arteriosus, as has classically been assumed, but two, the myocardial conus arteriosus and the non-myocardial bulbus arteriosus. From the evolutionary perspective, knowledge of the anatomy of the cardiac outflow tract of the holocephali is important, as they are the sister group of elasmobranchs. Our aim is to describe the cardiac outflow tract of four holocephalan species, two of them, Chimaera monstrosa and Hydrolagus affinis of the family Chimaeridae, and the other two, Harriotta raleighana and Rhinochimaera atlantica, of the family Rhinochimaeridae. The cardiac outflow tract of the four species consisted of a myocardial conus arteriosus, furnished with valves, and a bulbus arteriosus devoid of cardiac muscle. Both the bulbus and conus are tubular in shape. The length of the bulbus relative to the total length of the outflow tract is somewhat smaller in the rhinochimaerids (15%-19%) than in the chimaerids (19%-23%). The bulbus is covered by epicardium and is crossed by the main coronary artery trunks. Histologically, the bulbus is mainly composed of elastin and collagen, and, to a lesser extent, by smooth muscle. This suggests that in holocephalans, the bulbus actively helps to protect the gill vasculature from exposure to high-pressure pulses of blood. Our results prove that the bulbus arteriosus is common to chondrichthyans. In addition, they support the hypothesis that the cardiac outflow tract consisted of a conus arteriosus and a bulbus arteriosus from the beginning of the jawed vertebrate radiation, contributing to our understanding of the morphological changes that have occurred at the arterial pole of the heart in both actinopterygians and sarcopterygians.Proyecto CGL2010-16417/BOS; Fondos FEDE

Contribution of Xenopus model to a better understanding of cardiac outflow tract

Contribution of Xenopus model to a better understanding of cardiac outflow tract. A Torres-Prioris 1, SJ Smith 2, TJ Mohun 2, B Fernández 1, AC Durán 1. 1 Department of Animal Biology, Faculty of Science, and Biomedical Research Institute of Málaga (IBIMA), University of Málaga, Spain. 2 Developmental Biology Division, The Francis Crick Institute, Mill Hill Laboratory, London, UK. The morphology and morphogenesis of the cardiac outflow tract is a major topic in the study of the vertebrate circulatory system, especially regarding the pathologies affecting this region in humans. Recent studies have demonstrated that, in fish, the cardiac outflow tract consists of a myocardial conus arteriosus and a nonmyocardial bulbus arteriosus. Moreover, the bulbus arteriosus of fish has been considered homologous to the intrapericardial base of the aortic and pulmonary trunks of birds and mammals. Under this perspective, we have conducted a study on the outflow tract of Xenopus laevis, using histological, immunohistochemical and 3D reconstruction techniques. It has been assumed that the outflow tract of Xenopus, which is intercalated between the ventricle and the great arterial trunks, is of myocardial nature. At its luminal side, it contains two sets of valves between which the so-called spiral valve lies. Our results demonstrate that, together with a proximal myocardial segment, a distal, nonmyocardial, intrapericardial segment is also present in amphibians. We propose that this distal segment, from which the pulmocutaneous and systemic arteries arise, is homologous to the bulbus arteriosus of fish. Therefore, the bulbus arteriosus is an evolutionarily conserved structure, which has become the aortic and pulmonary roots of birds and mammals. Our findings contribute to strengthening Xenopus as a good model to better understand the outflow tract morphology and evolution, and as an emerging model for studying human congenital heart diseases. This work was supported by CGL2010-16417, BES-2011-046901, Estancias Breves para FPI (2012, 2013) and FEDER funds.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. CGL2010-16417, BES-2011-046901, Estancias Breves para FPI (2012, 2013), FEDER funds

The anatomical components of the cardiac outflow tract of the bichir, polypterus senegalus. Evolutionary significance

El resumen aparece en el Program & Abstracts of the 10th International Congress of Vertebrate Morphology, Barcelona 2013.Anatomical Record, Volume 296, Special Feature — 1: P-077.In chondrichthyans and actinopterygians, the outflow tract of the heart, namely, the cardiac portion intercalated between the ventricle and the ventral aorta, consists of two anatomical components: conus arteriosus and bulbus arteriosus. In chondrichthyans and extant representatives of phylogenetically ancient actinopterygian groups, the conus and bulbus are well-developed in size, whereas in most teleosts, the bulbus is markedly larger than the conus. Current knowledge about the cardiac outflow tract of the polypteriformes is scarce and highly contradictory, a fact that contrasts with their crucial phylogenetic position at the source of the actinopterygian lineage. In fact, it remains uncertain whether they have a bulbus at the arterial pole of the heart. The present study aimed to elucidate the anatomical arrangement of the cardiac outflow tract of the bichir in an attempt to improve our understanding of the evolution of the vertebrate heart. We examined the hearts from 12 bichirs using histochemical and immunohistochemical techniques. Our findings showed that the outflow tract of the bichir consists of two components, namely, a long conus arteriosus, largely composed of myocardial tissue and furnished with a variable number of valves at its luminal side, and a very short, elastin rich bulbus arteriosus, devoid of myocardium. The bulbus has an arterial-like histological composition. However, it differs from the aorta because it has a thicker wall, shows a different arrangement of the histological elements, is covered by the epicardium and is crossed by coronary arteries. The present observations are consistent with the notion that the conus arteriosus and the bulbus arteriosus have coexisted from the beginning of the jawed vertebrate radiation. This is of particular interest, because there is evidence that the bulbus arteriosus, which is a second heart field derivative, is homologous with the intrapericardial portions of the aorta and pulmonary artery of birds and mammals.Proyecto CGL2010-16417/BOS; Fondos FEDER

Anatomical, histochemical and immunohistochemical characterization of the outflow tract of ray hearts (Rajiformes; Chondrichthyes)

El resumen aparece en el Program & Abstracts of the 11th International Congress of Vertebrate Morphology, Washington DC 2016. Anatomical Record, Volume 299, Special Feature: 264.Recent work has shown that the cardiac outflow tract of sharks and chimaeras does not consist of a single myocardial component, the conus arteriosus, as classically accepted, but two, namely, the myocardial conus arteriosus and the non-myocardial bulbus arteriosus. However, the anatomical composition of the outflow tract of the batoid hearts remains unknown. The present study was designed to fill this gap. The material examined consisted of hearts of two species of rays, namely, the Mediterranean starry ray (Raja asterias) and sandy ray (Leucoraja circularis). They were studied using scanning electron microscopy, and histochemical and inmunohistochemical techniques. In both species, the outflow tract consists of two components, proximal and distal with regard to the ventricle. The proximal component is the conus arteriosus; it is characterized by the presence of compact myocardium in its wall and several transverse rows of pocket-shaped valves at its luminal side. Each valve consists of a leaflet and its supporting sinus. Histologically, the leaflet has two fibrosas, inner and outer, and a middle coat, the spongiosa. The distal component lacks myocardium. Its wall consists of smooth muscle cells, elastic fibers and collagen. Thus, it shows an arterial-like structure. However, it differs from the aorta because it is covered by the epicardium and crossed by coronary arteries. These findings indicate that the distal component is morphologically equivalent to the bulbus arteriosus of sharks and chimaeras. In contrast to foregoing descriptions, the valves of the first transverse row are distally anchored to the bulbus arteriosus and not to the ventral aorta. Our findings give added support to the notion that presence of a bulbus arteriosus at the arterial pole of the heart is common to all chondrichtyans, and not an apomorphy of actinopterygians as classically thought.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. CGL2014-52356-P, CEIMAR, BIO 203, FEDE

Is the bulbus arteriosus of fish homologous to the mamalian intrapericardial thoracic arteries?

El resumen aparece en el Program & Abstracts of the 10th International Congress of Vertebrate Morphology, Barcelona 2013.Anatomical Record, Volume 296, Special Feature — 1: P-089.Two major findings have significantly improved our understanding of the embryology and evolution of the arterial pole of the vertebrate heart (APVH): 1) a new embryonic presumptive cardiac tissue, named second heart field (SHF), forms the myocardium of the outflow tract, and the walls of the ascending aorta (AA) and the pulmonary trunk (PT) in mammals and birds; 2) the bulbus arteriosus (BA), previously thought to be an actinopterygian apomorphy, is present in all basal Vertebrates, and probably derives from the SHF. We hypothesized that the intrapericardial portions of the AA and the PT of mammals are homologous to the BA of basal vertebrates. To test this, we performed 1) a literature review of the anatomy and embryology of the APVH; 2) novel anatomical, histomorphological, and embryological analyses of the APVH, comparing basal (Galeus atlanticus), with apical (Mus musculus and Mesocricetus auratus) vertrebrates. Evidence obtained: 1) Anatomically, BA, AA, and PT are muscular tubes into the pericardial cavity, which connect the distal myocardial outflow tracts with the aortic arch system. Coronary arteries run through or originate at these anatomical structures; 2) Histologically, BA, AA, and PT show an inner layer of endothelium covered by circumferentially oriented smooth muscle cells, collagen fibers, and lamellar elastin. The histomorphological differences between the BA and the ventral aorta parallel those between intrapericardial and extrapericardial great arteries; 3) Embryologically, BA, AA, and PT are composed of smooth muscle cells derived from the SHF. They show a similar mechanism of development: incorporation of SHF‐derived cells into the pericardial cavity, and distal‐to‐proximal differentiation into an elastogenic cell linage. In conclusion, anatomical, histological and embryological evidence supports the hypothesis that SHF is a developmental unit responsible for the formation of the APVH. The BA and the intrapericardial portions of the great arteries must be considered homologous structures.Proyecto P10-CTS-6068 (Junta de Andalucía); proyecto CGL-16417 (Ministerio de Ciencia e Innovación); Fondos FEDER

PIGMENTATION OF THE HEART IN THE BICHIR, POLYPTERUS SENEGALUS

El resumen aparece en el Program & Abstracts of the 10th International Congress of Vertebrate Morphology, Barcelona 2013. Anatomical Record, Volume 296, Special Feature — 1: P-078.The presence of melanin-containing cells in the heart has been documented in tetrapods, but not in fish. It has been even suggested that dark pigmented cells are exclusively associated with hearts having two atria and two ventricles. The aim here is to report the occurrence of pigment cells in the heart of the bichir, an extant representative of the polypteriformes, an ancient ray-finned fish lineage that split from the stem of the actinopterygians soon after their divergence from the sarcopterygians. The bichir heart is composed of sinus venosus, atrium, ventricle, conus arteriosus and bulbus arteriosus arranged sequentially within the pericardial cavity. Dendritic-shaped cells containing melanosomes were found in the five cardiac components of the 12 bichirs included in this study. Numerous melanophores were distributed regularly over the surface of all segments having myocardium in their walls, thus resulting in a marked pigmentation of the whole heart. The bulbus arteriosus, which in the bichir is reduced in size, showed an even more intense pigmentation. In all instances, the melanophores were localized in the subepicardial space. Pigment cells also occurred in the pericardium and ventral aorta. The functional role of melanocytes in the tetrapod heart remains obscure. Antiinflamatory activity, cytoprotection and effects on the viscoelastic properties of the cardiac tissue have been adduced as possible actions of such cells. The role of pigment cells in the bichir heart constitutes a new open question. Interestingly, however, the only cells that have been shown to form melanin-containing cells in the heart derive from the neural crest. If the melanophores of the bichir heart are indeed of neural crest origin, it would suggest a much more extensive contribution and persistence of elements from the neural crest in the primitive heart of jawed vertebrates as assumed so far in most papers devoted to vertebrate heart embryology.Proyecto CGL2010-16417/BOS; Fondos FEDER; Beca FPI ref. BES-2011-046901

Moving Domain Computational Fluid Dynamics to Interface with an Embryonic Model of Cardiac Morphogenesis

Peristaltic contraction of the embryonic heart tube produces time- and spatial-varying wall shear stress (WSS) and pressure gradients (∇P) across the atrioventricular (AV) canal. Zebrafish (Danio rerio) are a genetically tractable system to investigate cardiac morphogenesis. The use of Tg(fli1a:EGFP)y1 transgenic embryos allowed for delineation and two-dimensional reconstruction of the endocardium. This time-varying wall motion was then prescribed in a two-dimensional moving domain computational fluid dynamics (CFD) model, providing new insights into spatial and temporal variations in WSS and ∇P during cardiac development. The CFD simulations were validated with particle image velocimetry (PIV) across the atrioventricular (AV) canal, revealing an increase in both velocities and heart rates, but a decrease in the duration of atrial systole from early to later stages. At 20-30 hours post fertilization (hpf), simulation results revealed bidirectional WSS across the AV canal in the heart tube in response to peristaltic motion of the wall. At 40-50 hpf, the tube structure undergoes cardiac looping, accompanied by a nearly 3-fold increase in WSS magnitude. At 110-120 hpf, distinct AV valve, atrium, ventricle, and bulbus arteriosus form, accompanied by incremental increases in both WSS magnitude and ∇P, but a decrease in bi-directional flow. Laminar flow develops across the AV canal at 20-30 hpf, and persists at 110-120 hpf. Reynolds numbers at the AV canal increase from 0.07±0.03 at 20-30 hpf to 0.23±0.07 at 110-120 hpf (p< 0.05, n=6), whereas Womersley numbers remain relatively unchanged from 0.11 to 0.13. Our moving domain simulations highlights hemodynamic changes in relation to cardiac morphogenesis; thereby, providing a 2-D quantitative approach to complement imaging analysis. © 2013 Lee et al

Cardiac myxosporiosis of pearl-spot, Etroplus suratensis (Bloch), due to Myxobolus etropli sp. nov.

A new myxosporea, Myxobolus etropli sp. now, was found to infect the bulbus arteriosus of Etroplus suratensis from brackishwarer lasoons of Muaulkadu. Chenna

Developmental temperature has persistent, sexually dimorphic effects on zebrafish cardiac anatomy

Over the next century, climate change of anthropogenic origin is a major threat to global biodiversity. We show here that developmental temperature can have significant effects on zebrafish cardiac anatomy and swimming performance. Zebrafish embryos were subjected to three developmental temperature treatments (T-D = 24, 28 or 32 degrees C) up to metamorphosis and then all maintained under common conditions (28 degrees C) to adulthood. We found that developmental temperature affected cardiac anatomy of juveniles and adults even eight months after the different thermal treatments had been applied. The elevation of T-D induced a significant increase of the ventricle roundness in juvenile (10% increase) and male (22% increase), but not in female zebrafish. The aerobic exercise performance of adult zebrafish was significantly decreased as T-D elevated from 24 to 32 degrees C. Gene expression analysis that was performed at the end of the temperature treatments revealed significant up-regulation of nppa, myh7 and mybpc3 genes at the colder temperature. Our work provides the first evidence for a direct link between developmental temperature and cardiac form at later life-stages. Our results also add to the emerging rationale for understanding the potential effects of global warming on how fish will perform in their natural environment